1 //===-- GenericOptional.cpp ----------------------------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===---------------------------------------------------------------------===//
8 
9 #include "Generic.h"
10 #include "LibCxx.h"
11 #include "LibStdcpp.h"
12 #include "Plugins/TypeSystem/Clang/TypeSystemClang.h"
13 #include "lldb/DataFormatters/FormattersHelpers.h"
14 #include "lldb/Target/Target.h"
15 
16 using namespace lldb;
17 using namespace lldb_private;
18 
19 bool lldb_private::formatters::GenericOptionalSummaryProvider(
20     ValueObject &valobj, Stream &stream, const TypeSummaryOptions &options) {
21   stream.Printf(" Has Value=%s ",
22                 valobj.GetNumChildren() == 0 ? "false" : "true");
23 
24   return true;
25 }
26 
27 // Synthetic Children Provider
28 namespace {
29 
30 class GenericOptionalFrontend : public SyntheticChildrenFrontEnd {
31 public:
32   enum class StdLib {
33     LibCxx,
34     LibStdcpp,
35   };
36 
37   GenericOptionalFrontend(ValueObject &valobj, StdLib stdlib);
38 
39   size_t GetIndexOfChildWithName(ConstString name) override {
40     return formatters::ExtractIndexFromString(name.GetCString());
41   }
42 
43   bool MightHaveChildren() override { return true; }
44   size_t CalculateNumChildren() override { return m_has_value ? 1U : 0U; }
45 
46   ValueObjectSP GetChildAtIndex(size_t idx) override;
47   bool Update() override;
48 
49 private:
50   bool m_has_value = false;
51   StdLib m_stdlib;
52 };
53 
54 } // namespace
55 
56 GenericOptionalFrontend::GenericOptionalFrontend(ValueObject &valobj,
57                                                  StdLib stdlib)
58     : SyntheticChildrenFrontEnd(valobj), m_stdlib(stdlib) {
59   if (auto target_sp = m_backend.GetTargetSP()) {
60     Update();
61   }
62 }
63 
64 bool GenericOptionalFrontend::Update() {
65   ValueObjectSP engaged_sp;
66 
67   if (m_stdlib == StdLib::LibCxx)
68     engaged_sp = m_backend.GetChildMemberWithName("__engaged_");
69   else if (m_stdlib == StdLib::LibStdcpp)
70     engaged_sp = m_backend.GetChildMemberWithName("_M_payload")
71                      ->GetChildMemberWithName("_M_engaged");
72 
73   if (!engaged_sp)
74     return false;
75 
76   // _M_engaged/__engaged is a bool flag and is true if the optional contains a
77   // value. Converting it to unsigned gives us a size of 1 if it contains a
78   // value and 0 if not.
79   m_has_value = engaged_sp->GetValueAsUnsigned(0) != 0;
80 
81   return false;
82 }
83 
84 ValueObjectSP GenericOptionalFrontend::GetChildAtIndex(size_t _idx) {
85   if (!m_has_value)
86     return ValueObjectSP();
87 
88   ValueObjectSP val_sp;
89 
90   if (m_stdlib == StdLib::LibCxx)
91     // __val_ contains the underlying value of an optional if it has one.
92     // Currently because it is part of an anonymous union
93     // GetChildMemberWithName() does not peer through and find it unless we are
94     // at the parent itself. We can obtain the parent through __engaged_.
95     val_sp = m_backend.GetChildMemberWithName("__engaged_")
96                  ->GetParent()
97                  ->GetChildAtIndex(0)
98                  ->GetChildMemberWithName("__val_");
99   else if (m_stdlib == StdLib::LibStdcpp) {
100     val_sp = m_backend.GetChildMemberWithName("_M_payload")
101                  ->GetChildMemberWithName("_M_payload");
102 
103     // In some implementations, _M_value contains the underlying value of an
104     // optional, and in other versions, it's in the payload member.
105     ValueObjectSP candidate = val_sp->GetChildMemberWithName("_M_value");
106     if (candidate)
107       val_sp = candidate;
108   }
109 
110   if (!val_sp)
111     return ValueObjectSP();
112 
113   CompilerType holder_type = val_sp->GetCompilerType();
114 
115   if (!holder_type)
116     return ValueObjectSP();
117 
118   return val_sp->Clone(ConstString("Value"));
119 }
120 
121 SyntheticChildrenFrontEnd *
122 formatters::LibStdcppOptionalSyntheticFrontEndCreator(
123     CXXSyntheticChildren *, lldb::ValueObjectSP valobj_sp) {
124   if (valobj_sp)
125     return new GenericOptionalFrontend(
126         *valobj_sp, GenericOptionalFrontend::StdLib::LibStdcpp);
127   return nullptr;
128 }
129 
130 SyntheticChildrenFrontEnd *formatters::LibcxxOptionalSyntheticFrontEndCreator(
131     CXXSyntheticChildren *, lldb::ValueObjectSP valobj_sp) {
132   if (valobj_sp)
133     return new GenericOptionalFrontend(*valobj_sp,
134                                        GenericOptionalFrontend::StdLib::LibCxx);
135   return nullptr;
136 }
137